Voltage divider assembly with thick film resistance elements

ABSTRACT

An assembly including a variable resistance comprising a resistive thick film for providing a variable voltage dividing function. The thick film is connectable across a source of voltage. A rotor mounted to make slidable contact with the thick film, provides an adjustable output voltage; and, the assembly includes a rectifier means for providing a feedback control voltage through the rectifier to the film.

United States Patent [191 Dumas Dec. 17, 1974 VOLTAGE DIVIDER ASSEMBLY WITH THICK FILM RESISTANCE ELEMENTS [75] Inventor: Christ J. Dumas, Forest View, 11].

[73] Assignee: American Plasticraft Company,

Chicago, Ill.

22 Filed: July 5,1973 21 -Appl. No.: 376,699

[52] U.S. Cl. 338/48, 338/174 [51] Int. Cl .Q. H0lc 9/02 [58] Field of Search 338/48, 174

[56] References Cited UNITED STATES PATENTS 3,585,559 6/l97l Rozema et a1. 338/48 Primary Examiner-Gerald Goldberg Attorney, Agent, or Firm-Leo J. Aubel 57 ABSTRACT An assembly including a variable resistance comprising a resistive thick film for providing a variable voltage dividing function. The thick film is connectable across a source of voltage. A rotor mounted to make slidable contact with the thick film, provides an adjustable output voltage; and, the assembly includes a rectifier means for providing a feedback control voltage through the rectifier to the film.

4 Claims, 6 Drawing Figures able contactor;

VOLTAGE-DIVIDER ASSEMBLY wITH THICK FILM RESISTANCE ELEMENTS BACKGROUND OF THE INVENTION Variable voltage dividers of various types are known in the art. Normally such voltage dividers .comprise a resistive path and means for varying the voltage across theresistive path or across portion of the resistive path.

It is an object of the present invention to provide a variable divider of small construction which includes a thick film resistance element formed on a substrate,

and has manual means for varying the voltage. Components for filtering the voltage developed across the resistance element, areincluded for providing a voltage which is a smooth, filtered DC. voltage.

It-isanother object of'the present invention to provide an improved voltage divider assembly having a conductive resistance film form on a ceramic substrate, having an adjustable contactor mounted on the substrate for varying effective resistance provided by the film, and capacitor components mounted on said substrate and electrically connected to theresistive path to provide a filtered'D.C. output which closely tracks a source voltage.

DESCRIPTION OF THE DRAWINGS FIG; Us a plan view of the substrate portion of a vari- 1 able voltage divider in accordancewith the invention;

FIG. 2 is a plan view of the rotor including the mov- FIG. 3 is a cross sectional view taken-along the lines 33'ofFlG. 2 showing .the'details of the rotor;

FIG. 4 is an isometric view of the voltage divider assembly in accordance with the'invention.

FIG.*5 is-a plan view showing an alternative embodiment of the substrate portion; and I a FIG. 6 is an electrical representation of the structure ofthe voltage divider of the invention.

DESCRIPTION OF THEINVENTION The presentvinvention is directed to a variable resistance voltage divider assembly comprising a thick film resistive path mounted on a substrate and having associated components for providing a stable output voltage relatively free of voltage spikes and transient excursions.

Referring now to' the drawings, the voltage divider assembly 11 comprises a housing 12, which in a preferred construction has a rectangularbottom portion 14 and a circular upper portion 16. A rotor 15 is mounted on a substrate 13.'The rotor 15 includes a centering pin l8-which is received in a center hole 23 in substrate 13. The rotor 15 includes a depending stop 4 19 which engages the shoulders 26 and 28 of substrate 13 to limit the extremes of its angular positions. An upstanding knob 2l on rotor 15 passes through a suitable central aperture 43 formed on the top of housing 12. Referring specifically-to FIG. 4, the substrate 13 forms thebottom of the assembly, and rotor 15 is positioned (sandwiched) between the substrate 13 and the hous- .ing12.

1 Housing 12, substrate 13 and rotor 15 are all formed ofsa non-conductive material such as for example ce- .ramic.

terminal connector pads 31 and 33 respectively. Note,

that the path 25 can be extended at either or both ends toward the pads 31 and 33. Pads 31 and 33 are formed of a conductive material deposited on substrate 13, and include suitable extensions for connection to the associated electronic carcuitry.

The rotor 15 includes a metalic conductive spring contactor or tap 20 which is formed and constrained to be anchored to the rotor such as by pin 18 and depending segments 40 and to be moved thereby. Contactor or tap 20 includes an end portion 22 whichslidably contacts the resistive path 25 to provide an electrical connection thereto. The other end 38 of the contactor 20 contacts a suitable conductor material 24 deposited or formed on the substrate 13.

-A circuit of electronic components comprising serially connected capacitor 37, diode 39 and capacitor 41, may be connected between connectors 27 and 29. Other electronic components such asthe impedance 30 indicated by the dotted line can be connected as shown. In the latter case, the capacitor 37 would be connected to the impedance 30, thence to connector -27.

1 FIG. 6 shows a schematic diagram of the voltage divider ll circuit arrangement and is useful in explaining the electrical operation of the circuitry. One use for such circuit is a centering circuit in television receivers. The resistive path 25, essentially a potentiometer having one terminal 31 connected to an AC. source such as a transformer and the other terminal 33 connected to the horizontal deflection yoke of the picture tube. develops a voltage thereacross. The diode 39 has its cathode connected to a midpoint on resistive path 25 and its anode connected to the readily adjustable contactor' 20 through the conductive connector 36 and collector 24. Diode 39 may also be connected in an opposite polarity, that is, its anode electrde connected to the midpoint on resistive path 25 and its cathode electrode connected to contactor 20.

In operation, diode 39 rectifies a portion of the current flowing through the resistive path 25 and couples this rectified current through the adjustable tap 20 back to the resistive path 25 to provide a DC. bias. The

' DC. voltage or bias supplied to the deflection yoke can thus be changed causing the center of deflection of the picture or raster to be changed. The voltate divider 11 thus provides the capability of controlling both the right and left movement of the raster.

The resistance of the resistive path 25 and the polarity connection of diode 39 depends on the voltage desired and the amount of centering required. In one embodiment a 20 ohm resistive path is used to obtain plus or minus one-half inch center variation of the picture positioning.

Capacitors 37 and 41, of a relatively low capacitance, function as transient filter capacitors to suppress any spikes (voltage transients) which may be produced by the diode at the voltage transition points. In certain instances where any spiking by the diode may be tolerated or acceptable, either or both capacitors may not be necessary.

A conductive connector (lead) 35 similar to connectors 27 and 29 electrically connects a midpoint of resistive path to the junction of diode 39 and capacitor 41.

Note, that metallic contactor 20 is bowed along its center portion as shown in FIG. 3 so that there is no electrical contact between contactor 20 and connector 35.

Another embodiment of the invention is shown in FIG. wherein the center contactor 24A is a resistive material and includes a resistance 32 which may either a discrete resistance or of a deposited material similar to resistive path 25. Resistance 32 is connected either directly or through conductive connector 36A to a third terminal pad 42 in turn connected to the junction of capacitor 37 and diode 39. The resistor 32 functions as a pulse limiter during adjustment.

The terminal pad 42 is useful to provide a means to connect a selected voltage from the yoke, to effect feedback control to compensate for picture changes due to station or receiver phase changes.

While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that changes in form and details may be made without departing from the spirit and scope of the invention.

What is claimed is:

l. A variable voltage divider comprising an electrically non-conductivesubstrate, a plurality of conductive terminations supported on a surface of said substrate, a resistive path supported on said surface and electrically connected at its ends to respective conductive terminations, a first conductive connector supported on said surface and having one end electrically connected to a intermediate point on said resistive path, a center conductive collector supported on said surface, adjusting means supported for movement relative to the substrate, a conductive contactor constrained to move with the adjusting means to wipingly engage the resistive path and the conductive collector, a second conductive connector having one end connected to the collector, rectifier means having one electrode connected to said first conductive connector and the other electrode connected to the conductive contactor and the collector to thereby provide a variation in the output voltage and a feedback control voltage bias.

2. A variable voltage divider as in claim I further in cluding at least one capacitor connected to said rectifier means to filter the voltage appearing there across.

3. A variable voltage divider as in claim 1 wherein said conductive collector comprises a thick film resistance.

4. A variable volage divider as in claim 2 wherein a conductive termination is connected to the junction of the capacitor and the rectifier means with the moveable connector to provide a selected output voltage. 

1. A variable voltage divider comprising an electrically nonconductive substrate, a plurality of conductive terminations supported on a surface of said substrate, a resistive path supported on said surface and electrically connected at its ends to respective conductive terminations, a first conductive connector supported on said surface and having one end electrically connected to a intermediate point on said resistive path, a center conductive collector supported on said surface, adjusting means supported for movement relative to the substrate, a conductive contactor constrained to move with the adjusting means to wipingly engage the resistive path and the conductive collector, a second conductive connector having one end connected to the collector, rectifier means having one electrode connected to said first conductive connector and the other electrode connected to the conductive contactor and the collector to thereby provide a variation in the output voltage and a feedback control voltage bias.
 2. A variable voltage divider as in claim 1 further including at least one capacitor connected to said rectifier means to filter the voltage appearing there across.
 3. A variable voltage divider as in claim 1 wherein said conductive collector comprises a thick film resistance.
 4. A variable volage divider as in claim 2 wherein a conductive termination is connected to the junction of the capacitor and the rectifier means with the moveable connector to provide a selected output voltage. 